This project will test a group of simple models of fertility, nuptiality and mortality change in nineteenth-century America. We will date the transition to lower fertility and mortality, investigate the impact of changes in the standard of living on mortality, and compare several hypotheses which explain the fertility These hypotheses emphasize the availability of land, the assimilation of immigrants, and the demographic modernization of the population. We will take a regional approach examining places where there were natives and immigrants, where there was some evi- dence of modernization, and where the frontier was moving so that we can see changing patterns of land availability. Rural Texas will be our focus. The project will make use of linked individual- level data to overcome the lack of civil vital registration data. We will build life histories by linking data drawn from the manuscript censuses, church vital registration, the limited civil vital registration which exists, and tax records. The project will develop a system of analytic software for these data, using two strategies. On one side we will use the kinds of analytic strategies used for family reconstitution data, and for the life history data collected from population registers. On the other side we will make use of methods devised for the analysis of census data, such as own-children fertility measures and census- survival mortality measures. This project will relate rural mortality change to changes in its age-specific structure and its relationship to standards of living. We propose three simple models of fertility change. The first is the "Land Availability-Wealth Flows" hypothesis, which is based on work which relates fertility and nuptiality to the availability of land. The second is the "Immigrant Assimilation" hypothesis, which argues that high-fertility immigrants became assimilated to lower American fertility. The third hypothesis is "Demographic Modernization," and it is based on relationships between education, technology and urbanization and fertility. We propose to treat and reformulate these.